Answer
1.47.
Work Step by Step
For a plane refracting surface, $\frac{n_a}{s}+\frac{n_b}{s’}=0$.
Light is coming from the object. We know that s = 3.60 m and we are looking for $n_a$. The image is formed by light in the air, so $n_b = 1.00$ and s’ = –2.45 m.
$$\frac{n_a}{s}+\frac{n_b}{s’}=0$$
$$\frac{n_a}{3.60m}+\frac{1.00}{-2.45m}=0$$
$$ n_a =(3.60m)\frac{1.00}{2.45m}=1.47$$
